Kilo-Tesla magnetic fields in the magnetic vortex acceleration regime – a prospective experimental diagnostic

Magnetic Vortex Ion Acceleration (MVA) is characterized by the self-generation of a strong azimuthal magnetic field (up to hundreds of kilo-Tesla) in the interaction of ultraintense laser-beams with near-critical-density (NCD) targets. Experimental validation of kilo-Tesla magnetic fields could provide a more profound understanding not only of MVA, but also of fusion processes where strong magnetic fields may be generated (Ruhl and Korn, arXiv:2202.03170v5, 2022).

Here, we propose an experimental diagnostic to measure the temporal (sub-ps) and spatial distribution of kilo-Tesla magnetic fields generated at the rear side of NCD targets under single-pulse, ultrashort (45 fs) laser-plasma interactions. This technique is based on the Faraday rotation induced on an initially linearly polarized probe beam propagating through a strong parallel magnetic field in a plasma and on the imaging of the associated projected polarization states. 2D simulations were performed using relativistic particle-in-cell code to numerically explore the magnetic field generated under MVA regime in boron-like-fusion targets and the resulting Faraday rotation. The simulation and analytical results demonstrate that this diagnostic may be experimentally implemented in existing laser facilities.